SERE (1994) classified and concisely characterised world livestock production systems into 11 groupings, as the basis for this series of studies. Six of these groupings are characterised by significant crop-livestock interactions, and are summarised in Table 1. Ruminants are the major livestock species interacting with cropping. Poultry are also important sources of meat and eggs, but the major supply route is through specialised intensive systems rather than mixed systems. Pigs are highly valued in regions such as South-East Asia but, again, apart from scavenging systems, the major feed inputs are concentrate rations. The impact of these systems on the environment is covered in depth in the report on “Demand for Feed Concentrates”.
For the purpose of this study, mixed farming systems are defined according to MORTIMORE (1991) ie. where both livestock and crop production take place within the same locality, and where ownership of crops or land and livestock are integrated. However, where specialised livestock production takes place in the same locality as crop production, subject to resource-sharing (e.g. grazing of residues), but under separate ownership, such systems may be included.
